Damocles

Damocles (dămˈəklēz) [key], in classical mythology, courtier at the court of Dionysius I. He so persistently praised the power and happiness of Dionysius that the tyrant, in order to show the precariousness of rank and power, gave a banquet and had a sword suspended above the head of Damocles by a single hair. Hence the expression "the sword of Damocles" to mean an ever-present peril.